When an object is heated to a high temperature it emits light that is more characteristic of its temperature than of its composition. At this point we call the object a blackbody radiator. Some characteristics of the light emitted by these objects are:
1. a continuous spectra (over a wide range of wavelengths) is produced
2. the wavelength of maximum radiation intensity varies inversely with the temperature
3. the total energy emitted varies as the fourth power of the temperature (E T 4)
4. the power at a given temperature varies inversely with the fifth power of the wavelength (P -5)
These characteristics result in emission spectra like those below.
The 5000 K line in the figure corresponds roughly to the temperature of the sun and the 3000 K line corresponds roughly to the temperature of a tungsten filament light bulb. Note that light is being given off at all the visible wavelengths. Below is what a blackbody emission spectra, in a form more like we have seen before, might look like (this one is at 6000 K). This is very similar to what the solar spectrum looks like.